Texture-Based MRI Analysis Reveals Microstructural Alterations and Lateralization in the Putamen in Bipolar Disorder

Background and Objectives: Bipolar disorder (BD) is associated with widespread neuroanatomical alterations, particularly within subcortical structures involved in emotional regulation. Conventional magnetic resonance imaging (MRI) approaches may fail to detect subtle microstructural changes. This study aimed to evaluate histogram-based texture characteristics of the putamen in patients with BD and to compare these findings with those of healthy controls. Materials and Methods: This retrospective cross-sectional study included 66 participants (33 BD patients, 33 controls). All subjects underwent standardized cranial MRI. Regions of interest corresponding to the putamen were manually delineated, and histogram-based texture parameters were extracted using custom-developed software. Group comparisons were performed using appropriate statistical tests based on data distribution. Results: The groups were comparable in age and sex (p > 0.05). Significant differences were observed in multiple texture parameters, particularly in the left putamen. Mean and median values were significantly higher in BD patients compared to controls (511.19 ± 106.96 vs. 440.68 ± 102.21, p = 0.008; 511.92 ± 106.71 vs. 440.53 ± 102.74, p = 0.007). Minimum intensity values and root-sum-of-squares levels were also significantly increased (p < 0.001). Skewness differed significantly (p = 0.004), indicating altered distribution asymmetry. Percentile analyses demonstrated consistent differences across nearly all levels, suggesting a shift in intensity distribution. Additionally, Katz fractal dimension was significantly lower in BD patients (p < 0.001), indicating reduced structural complexity. Similar but less pronounced alterations were observed in the right putamen. Overall, findings suggest the presence of widespread alterations in intensity distribution and structural characteristics. Conclusions: Patients with BD exhibit significant alterations in putamen texture parameters, potentially reflecting alterations in intensity distribution and texture-derived structural characteristics. These changes are more prominent in the left hemisphere, suggesting potential lateralization. Histogram-based texture analysis may provide a sensitive, non-invasive approach for detecting subtle brain alterations in BD and may serve as a complementary neuroimaging biomarker.